Anyone who voluteers to go fight in someone else's war for anything other than significant money is an "extremist." After all, what could be more extreme behavior?

But to assume these people are radicalized, or proponents for some extreme perspective on Islam is an assumption without basis in logic or fact. Most probably believe in the principle of self-determination; and where legal democracy is either illegal or ineffective, then only "illegal democracy" remains. Insurgency only differs from democracy by legality. This is civil disobedience taken to the extremes because taking it to the extremes is the only viable option for change.

One need not agree, but one should respect those who answer that call. Even if one's mission is to stop them from succeeding.